Why the emptiness brings fear in to our mind?

Time to time , feeling emptiness, do not see any value in goodness and badness. Some time, getting the question what is happiness, everything seems to be happiness, everything seems to be annoying. Feeling like to cry some times. But at the end, feeling some kind of fear in my mind whenever i get feel the mentioned above. What is the practice, or what is that have to be done to understand or overcome this fear?